I carry 1911's, cocked and locked.
All of the holsters I use have a thumb break.
Here's and example.
http://www.cabelas.com/product/Galco-Le ... 744659.uts
The thumb break aids retention and reduces to virtually nil the chance of a negligent discharge. Mine are pretty ancient pieces of well maintained leather(newest holster is old enough to vote).
I carry owb at 3:00 w/double mag carrier at 9:00, and have done so concealed and open for decades. The only thing that changes in my gear, open to concealed, is use of a cover garment.
Muscle memory, after uncounted thousands of draw strokes, brings my thumb to the break and then down to the grip without conscious effort. I know that I can quickly and surely draw my pistol if the need arises.
When I have open carried, 95% of the folks wandering around in public never even see the pistol. They don't expect a well dressed, clean cut, old fat guy to have one and it just never registers. Of the 5% who do see the pistol, most assumed that I was a LEO or the like(I've heard comments on my age, physical condition, etc. for a police officer) The remaining just avoid me.
I have never been confronted by anyone, LEO, Security or Concerned Citizen about carrying the pistol. There have been two (2) curious guys over the years who have asked about my CBOB.